Photoluminescent fibers, compositions and fabrics made therefrom

ABSTRACT

Disclosed are photoluminescent fibers containing photoluminescent phosphorescent materials and photoluminescent fluorescent materials which emit electromagnetic energies to give an emission signature. Also disclosed are the use of the inventive fibers, fabrics made therefrom, and objects containing the fiber.

This application is a continuation of co-pending U.S. patent applicationSer. No. 12/479,514, filed on Jun. 5 2009, entitled, “PHOTOLUMINESCENTFIBERS, COMPOSITIONS AND FABRICS MADE THEREFROM,” which in turn claimspriority to U.S. Provisional Patent Application Ser. No. 61/129,126,filed on Jun. 5, 2008, entitled, “Photoluminescent fibers compositions,methods, use and fabric made therefrom,” each of which are incorporatedby reference herein in their entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates generally to the field of photoluminescentfibers. In particular, the present invention relates to photoluminescentphosphorescent fibers whose emission signature lies partly or fully inthe infrared region of the electromagnetic spectrum. The presentinvention also relates to the use of the inventive fibers, fabrics madetherefrom, and objects containing the fiber.

BACKGROUND OF THE INVENTION

Photoluminescent materials and compositions that containphotoluminescent phosphorescent materials with emissions in the visibleregion of the electromagnetic spectrum have been disclosed. For example,metal sulfide pigments which contain various elemental activators,co-activators and compensators have been prepared which absorb at380-400 nm and have an emission spectrum of 450-520 nm.

Recently, phosphorescent materials that have significantly higherpersistence, up to 12-16 hours, have been reported. Such phosphorsgenerally comprise an alkaline earth aluminate host matrix and can berepresented, for example, by MAl₂O₃ or MAl₂O₄ wherein M can comprise aplurality of metals, at least one of which is an alkaline earth metal,such as calcium, strontium, barium and magnesium. These materialsgenerally deploy Europium as an activator and can additionally alsocontain one or more rare earth materials as co-activators. Examples ofsuch high intensity and high persistence phosphors can be found, forexample, in U.S. Pat. Nos. 5,424,006, 5,885,483, 6,117,362 and 6,267,911B1.

Photoluminescent compositions comprising only phosphorescent materialswith emissions in the infrared region have been reported. Suchphosphorescent materials consist of doped ZnCdS. These materials havebeen shown to have observable tail emissions into the visible region andconsequently would not have utility for clandestine markings. Thesematerials have neither been used for clandestine detection or fordetection applications wherein activation and detection can be decoupledspatially and temporally.

Photoluminescent compositions which contain combinations of ZnSphosphorescent materials and fluorescent materials have also beendisclosed. However the use of these fluorescent materials has beenlimited to either altering the charging (activating) radiation oraltering the visible daylight or visible emission color. Use of ZnS withfluorescent materials is generally limited to altering the colorobserved in daylight.

Photoluminescent compositions have also been contemplated which containa series of fluorescent materials. One of the fluorescent materialsabsorbs and emits radiation which is then absorbed by a companionfluorescent material which then emits radiation to give a final infraredemission. As can be appreciated, use of fluorescent materials does notprovide for any continued emission once the absorbable radiation isremoved. These compositions have no provision for continued emission ofinfrared radiation that can be detected at a future time, that is, afteractivation has ceased. The need for activating the materials immediatelyprior to detection will also require possession of activating equipmentat site of detection thereby limiting flexibility and/or portability andthus will not permit stealth detection.

Prior art in the field of photoluminescent fibers has focused entirelyon visible emission such as U.S. Pat. Nos. 5,674,437; 6,162,539,7,338,877 and 6,307,207B1. No work has been reported for creatingphotoluminescent fibers with emissions partly or fully in the infraredregion of the electromagnetic spectrum.

Although methods for uniquely marking and identifying objects havereceived thought and attention, such methods do not enable stealthdetection. In many cases, such as, for example, identification offriendly forces in the combat theater, the identifying markings need tobe unobservable by enemy personnel, or, for example, in anti-counterfeitapplications wherein, the identifying markings need to be hidden toavoid detectability of such markings by counterfeiters. Clandestine orstealth identification, wherein the emissions from the photoluminescentmarkings are not ordinarily observable by a human observer (withoutspecific detection equipment), but detectable by friendly forces, andfurther wherein activation is not required during detection (suchactivation being potentially detectable by others), will be of highvalue in the combat theater for stealth detection of combat equipment,or personnel. Such markings will also be of value for stealth combatoperations, or for covertly marking enemy targets for tracking orelimination.

There is no mention in the literature of fibers that photoluminescefully or partially in the infrared region of the electromagneticspectrum. Therefore there are no fabrics which contain these fibers thatcould be used for clandestine or stealth identification, or where thesefibers could be used for authentication purposes.

As can be seen from the above discussion, there is a need forphotoluminescent fibers, fabrics made therefrom and objects containingthe fiber which emit partly or fully in the infrared region of theelectromagnetic spectrum useful for identification and detection ofobjects. Furthermore there is also a need for photoluminescent fibers,fabrics made therefrom and objects containing the fiber that enable theact of detection of the object to be decoupled spatially from the objectand/or its activation source, that is, detection can occur away from theobject and/or its activation source, and also wherein, detection can bedecoupled temporally from activation, that is, detection can occur at atime later than the activation. It should be noted that decoupling ofactivation and detection also allows for flexibility and portability inthe act of detection, allowing for clandestine or stealth identificationand detection.

SUMMARY OF THE INVENTION

The present invention provides for photoluminescent fibers containingphotoluminescent phosphorescent materials and photoluminescentfluorescent materials whose emission signature lies partly or fully inthe infrared region of the electromagnetic spectrum. As well, theinvention provides for photoluminescent fibers containingphotoluminescent phosphorescent materials and photoluminescentfluorescent materials whose emission signature lies partly or fully inthe infrared region of the electromagnetic spectrum which are high inintensity and high in persistence. The present invention also providesfor fabrics that incorporate these fibers either as the only fiber orinterwoven with non-photoluminescent fibers.

A key advantage of these photoluminescent fibers, such as thosedescribed below, is that they can be activated or excited withoutrequiring specialized sources. That is, the photoluminescent fibers canbe charged with naturally-occurring illumination essentially for most ofthe day be it during the morning, noon, or evening, as well as on cloudydays. The present invention therefore eliminates the need for activatingequipment at the point of identification or detection. Further, with theuse of high emission intensity and persistent photoluminescentcompositions, such as those described below, methods of identifying ordetecting objects can be practiced also at nighttime, that is, longafter activation has ceased, and at great distances.

In a first aspect, the present invention provides for photoluminescentfibers containing one or more photoluminescent phosphorescent materialsand one or more photoluminescent fluorescent materials wherein the oneor more photoluminescent phosphorescent materials are selected so thatthey absorb and emit electromagnetic energies when charged or activatedby either electromagnetic radiation from an excitation source incidentupon the composition, or by emission of another photoluminescentmaterial, or both, and wherein the one or more photoluminescentfluorescent materials are selected so that they absorb the emission fromthe one or more photoluminescent materials and emit electromagneticenergies to give a selected emission signature, such that some or all ofthe emission signature lies in the infrared portion of theelectromagnetic spectrum, the photoluminescent materials being selectedso that the emission of one of the photoluminescent materials overlapswith the absorbance of another of the photoluminescent materials,wherein the selected emission signature is the emission from one or moreof the selected photoluminescent fluorescent materials, such emissionbeing essentially unabsorbed by any of the other photoluminescentmaterials.

In a second aspect, the present invention provides for a fibercontaining a core and a sheath, wherein the core containsphotoluminescent phosphorescent materials and optionallyphotoluminescent fluorescent materials and the sheath containsphotoluminescent fluorescent materials.

In a third aspect, the present invention provides for a fiber containinga core and a sheath, wherein the core contains both photoluminescentphosphorescent materials and photoluminescent fluorescent materials andthe sheath contains materials that shift the color of the fiber, maskthe fiber, protect the fiber or a combination thereof.

In a fourth aspect, the present invention provides for a fibercontaining a core, a sheath and a second sheath, wherein the corecontains photoluminescent phosphorescent materials and optionallyphotoluminescent fluorescent materials and the sheath containsphotoluminescent fluorescent materials and the second sheath containsphotoluminescent fluorescent materials.

In a fifth aspect, the present invention provides for a fiber containinga core, a sheath and a second sheath, wherein the core containsphotoluminescent phosphorescent materials and optionallyphotoluminescent fluorescent materials and the sheath containsphotoluminescent fluorescent materials and the second sheath containsmaterials that shift the color of the fiber, mask the fiber, protect thefiber or a combination thereof.

In a sixth aspect, the present invention provides for a fiber containinga core, a sheath and a second sheath, wherein the core is reflective ofphotoluminescent emission, a strengthening fiber, a conductive fiber oran optical fiber and the sheath contains photoluminescent phosphorescentmaterials and optionally photoluminescent fluorescent materials and thesecond sheath contains photoluminescent fluorescent materials.

In a seventh aspect, the present invention provides for a fibercontaining a core, a sheath, a second sheath and a third sheath, whereinthe core contains photoluminescent phosphorescent materials andoptionally photoluminescent fluorescent materials, the sheath containsphotoluminescent fluorescent materials, the second sheath containsphotoluminescent fluorescent materials and the third sheath containsphotoluminescent fluorescent materials.

In an eighth aspect, the present invention provides for a fibercontaining a core, a sheath, a second sheath and a third sheath, whereinthe core contains photoluminescent phosphorescent materials andoptionally photoluminescent fluorescent materials, the sheath containsphotoluminescent fluorescent materials, the second sheath containsphotoluminescent fluorescent materials and the third sheath containsmaterials that shift the color of the fiber, mask the fiber, protect thefiber or a combination thereof.

In a ninth aspect, the present invention provides for a fiber containinga core, a sheath, a second sheath and a third sheath, wherein the coreis reflective of photoluminescent emission, a strengthening fiber, aconductive fiber or an optical fiber, the sheath containsphotoluminescent phosphorescent materials and optionallyphotoluminescent fluorescent materials, the second sheath containsphotoluminescent fluorescent materials and the third sheath containsmaterials that shift the color of the fiber, mask the fiber, protect thefiber or a combination thereof.

In a tenth aspect, the present invention provides for fabrics made fromthe aforementioned aspects.

In an eleventh aspect, the present invention provides for methods ofstealth detection and identification using the fibers and fabrics of theaforementioned aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a shift in emission spectra resulting fromincorporation of photoluminescent phosphorescent and photoluminescentfluorescent dyes. Chart a) is the representative absorbance spectra, b)is the representative emission spectra and c) is the representative netemission spectra resulting from the inventive composition. Asillustrated a photoluminescent phosphorescent material absorbs radiationat A1 from an excitation source. The photoluminescent phosphor cancontinuously emit radiation E1 which overlaps with the absorptionspectra A2 which emits radiation at E2. E2 again is designed to overlapwith the absorption A3 which emits radiation E3. This process cancontinue until a final desired emission is obtained, in this case E5. Ascan be seen from chart c) the composition is designed to emit radiationat approx. 780 nm.

FIG. 2 illustrates a singled stranded fiber of the current inventionwhich contains the photoluminescent phosphorescent and photoluminescentfluorescent materials.

FIG. 3 illustrates a fiber of the current invention with a core (10) anda sheath (12).

FIG. 4 illustrates a fiber of the current invention with a core (10), asheath (12) and a second sheath (14).

FIG. 5 illustrates a fiber of the current invention with a core (10), asheath (12), a second sheath (14) and a third sheath (16).

DETAILED DESCRIPTION OF THE INVENTION

It has been found that photoluminescent compositions comprisingphotoluminescent phosphorescent and photoluminescent fluorescentmaterials whose emission signature lies partly or fully in the infraredregion of the electromagnetic spectrum when made into fibers, fabricsmade from the fibers or objects incorporating the fibers permitidentification or detection. A key advantage of the use of thephotoluminescent phosphorescent fibers is that they can be activated orexcited without requiring specialized sources. That is, they can becharged with naturally-occurring illumination essentially for most ofthe day, be it during the morning, noon, or evening, as well as oncloudy days in addition to artificial sources such as metal halidelamps. Whether activated by naturally or artificially occurringillumination the present invention eliminates the need for havingactivating equipment at the point of identification or detection andenables detection to be practiced at daytime or nighttime and atlocations away from the fiber, and/or its detection source as well asafter the activation of the fiber has ceased. Further, with the use ofhigh luminous intensity and persistent photoluminescent phosphorescentcompositions, such as those described below, fiber identification ordetection at daytime or nighttime can be practiced at great distancesfrom the fiber and/or its activation source and long after activationhas ceased.

Unless otherwise noted, percentages used herein are expressed as weightpercent.

As used herein, a “luminescent” material is a material capable ofemitting electromagnetic radiation after being excited into an excitedstate.

As used herein, a “photoluminescent composition” is defined as anadmixture of materials which is capable of emitting electromagneticradiation from electronically-excited states when excited or charged oractivated by electromagnetic radiation.

As used herein, a “fluorescent” material is a material that has theability to be excited by electromagnetic radiation into an excited stateand which releases energy in the form of electromagnetic radiationrapidly, after excitation. Emissions from fluorescent materials have nopersistence, that is, emission essentially ceases after an excitationsource is removed. The released energy may be in the form of UV, visibleor infrared radiation.

As used herein, a “phosphorescent” material is a material that has theability to be excited by electromagnetic radiation into an excitedstate, but the stored energy is released gradually. Emissions fromphosphorescent materials have persistence, that is, emissions from suchmaterials can last for seconds, minutes or even hours after theexcitation source is removed. The released energy may be in the form ofUV, visible or infrared radiation.

“Luminescence”, “phosphorescence” or “fluorescence” is the actualrelease of electromagnetic radiation from a luminescent, phosphorescentor fluorescent material, respectively.

As used herein “Luminous Intensity” is defined as a measure of emittedelectromagnetic radiation as perceived by a “standard observer” (seee.g. C. J. Bartelson and F. Grum, Optical Radiation Measurements, Volume5—Visual Measurements (1984), incorporated herein by reference) asmimicked by a photoptic detector, such as an IL 1700Radiometer/Photometer with high gain luminance detector by InternationalLight Co of Massachusetts.

As used herein “emission intensity” is defined as a measure of thephotoluminescent emissions from a photoluminescent object, suchmeasurement being made with any device capable of measuring the emissionstrength either photometrically or radiometrically, such emissions beingeither visible or infrared or both.

As used herein “persistence” is defined as the time it takes, afterdiscontinuing irradiation, for photoluminescent emissions emanating froma photoluminescent object to decrease to the threshold detectabilitywith a suitable detection apparatus.

As used herein “high persistence” is defined to mean that the time ittakes, after discontinuing irradiation, for photoluminescent emissionsemanating from a photoluminescent object to decrease to the thresholddetectability with a suitable detection apparatus is greater than fivehours.

As used herein, “electromagnetic radiation” refers to a form of energycontaining both electric and magnetic wave components which includesultraviolet (UV), visible and infrared (IR) radiation.

As used herein, an “emission signature” refers to the specific emissionspectrum of the photoluminescent composition as a result of activation,such emission being characterizable by wavelength and amplitude.

As used herein “radiation incident upon the photoluminescentcomposition” refers to the activating or charging electromagneticradiation wherein at least some of the incident electromagneticradiation will initially excite one or more of the photoluminescentmaterials.

As used herein, “Stokes shift” refers to the difference in wavelengthbetween the excitation or activation wavelength and the emissionwavelength of photoluminescent materials.

As used herein, a “liquid carrier medium” is a liquid that acts as acarrier for materials distributed in a solid state and/or dissolvedtherein.

As used herein, a “stabilizing additive” is a material added to acomposition so as to uniformly distribute materials present asparticulates, to prevent agglomeration, and/or prevent settling of solidmaterial in a liquid carrier medium. Such stabilizing additivesgenerally comprise dispersants, and/or rheology modifiers.

As used herein, “rheology modifiers” are those substances whichgenerally can build viscosity in liquid dispersion compositions, thatis, compositions containing particulate matter distributed in a liquidcarrier, thereby retarding settling of such particulate materials, whileat the same time significantly lowering viscosity upon application ofshear, to enhance smooth applicability of such compositions ontoobjects.

As used herein, “dispersing agents” are those substances which are usedto maintain dispersed particles in suspension in a composition in orderto retard settling and agglomeration.

As used herein, “photostabilizers” refers to components of thecomposition designed to retard deterioration, degradation or undesirablechanges in compositional and/or visual properties as a result of actionsby electromagnetic radiation.

As used herein “clandestine or stealth identification” refers to the actof identifying or detecting a fiber, a fabric made therefrom or anobject containing the fiber, wherein the emissions from thephotoluminescent markings used for such identification or detection areordinarily not visible to a human observer either during daytime ornighttime and wherein the emissions from such photoluminescent markingsrequire specific detection equipment for observation for the purpose ofidentification or detection, and further wherein, activation or chargingis not required during detection.

As used herein “stealth marking” refers to a photoluminescent marking,including fibers, fabrics made therefrom, and objects containing thefiber, whose daylight color has been formulated so as not to bedistinguishable from the surrounding area.

As used herein “spatially and temporally decoupled” means that detectioncan be practiced after the activation has ceased (temporally) as well asdetection can occur away from the fiber, the fabric made therefrom orthe object containing the fiber and/or its activation source(spatially).

As used herein “CAS #” is a unique numerical identifier assigned toevery chemical compound, polymer, biological sequences, mixtures andalloys registered in the Chemical Abstracts Service (CAS), a division ofthe American Chemical Society.

As used herein “fiber” means a filament of finite length or of acontinuous structure and includes multicomponent compositions includingcore/sheath, eccentric core/sheath, trilobal core/sheath, side-by-side,mixed viscosity side-by-side, ABA side-by-side, trilobal side-by-side,tipped trilobal, tipped cross, segmented pie micro-denier,islands-in-the-sea micro-denier, striped micro-denier, and combinationsthereof, including hollow constructs.

Not to be held to theory, it is believed that, the selectedphotoluminescent phosphorescent materials absorb incident activatingelectromagnetic radiation, for example, ultraviolet and/or visibleportions of the electromagnetic spectrum, and an electron is excitedfrom a ground state into an excited state. The excited state electron ofa phosphorescent material undergoes a conversion called intersystemcrossing wherein the electron is trapped in the excited state and onlyslowly returns to the ground state with a subsequent emission ofelectromagnetic radiation, for example, in the visible region of theelectromagnetic spectrum. The time for emission to occur from theexcited state of phosphorescent materials can be on the order of 10⁻³seconds to hours and even days. In this manner emission radiation fromexcited phosphorescent materials can continue long after the incidentradiation has ceased.

The energy of the emission radiation from a photoluminescent material isgenerally of lower energy than the energy of the incident activatingradiation. This difference in energy is called a “Stokes shift”.

Phosphorescent materials suitable for the current invention include, forexample, the well known metal sulfide phosphors such as ZnCdS:Cu:Al,ZnCdS:Ag:Al, ZnS:Ag:Al, ZnS:Cu:Al as described in U.S. Pat. No.3,595,804 and metal sulfides that are co-activated with rare earthelements such as those describe in U.S. Pat. No. 3,957,678 as well asthe alkaline earth aluminate phosphors doped with europium and oftencomprise one or more co-activators such as elements of the Lanthanideseries (e.g. lanthanum, cerium, praseodymium, neodymium, samarium,gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium,and lutetium), tin, manganese, yttrium, or bismuth. Examples of suchphotoluminescent phosphors are described in U.S. Pat. No. 5,424,006.

Other phosphorescent materials useful in the current invention includethe alkaline earth aluminate oxides having the formula MO. mAl₂O₃:Eu²⁺,R³⁺ wherein m is a number ranging from 1.6 to about 2.2, M is analkaline earth metal (strontium, calcium or barium), Eu²⁺ is anactivator, and R is one or more trivalent rare earth materials of thelanthanide series (e.g. lanthanum, cerium, praseodymium, neodymium,samarium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, lutetium), yttrium or bismuth co-activators. Examples of suchphosphors are described in U.S. Pat. No. 6,117,362, as well as thealkaline earth aluminate oxides having the formula M_(k) Al₂O₄:2×Eu²⁺,2yR³⁺ wherein k=1-2x−2y, x is a number ranging from about 0.0001 toabout 0.05, y is a number ranging from about x to 3×, M is an alkalineearth metal (strontium, calcium or barium), Eu²⁺ is an activator, and Ris one or more trivalent rare earth materials (e.g. lanthanum, cerium,praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium,holmium, erbium, thulium, ytterbium, lutetium), yttrium or bismuthco-activators. Examples of such phosphors are described in U.S. Pat. No.6,267,911 B1.

Other phosphorescent materials suitable for this invention are alkalineearth aluminates of the formula MO.Al₂O₃.B₂O₃:R wherein M is acombination of more than one alkaline earth metal (strontium, calcium orbarium or combinations thereof) and R is a combination of Eu²⁺activator, and at least one trivalent rare earth material co-activator,(e.g. lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium),bismuth or manganese. Examples of such phosphors can be found in U.S.Pat. No. 5,885,483.

Phosphorescent materials described above generally absorb in the UV ornear UV/Visible regions of the electromagnetic spectrum with subsequentemissions from 390-700 nm.

As can be appreciated, many other phosphors are useful to the presentinvention. Such useful phosphors are described in Yen and Weber,Inorganic phosphors: compositions, preparation and optical properties,CRC Press, 2004.

Not to be held to theory the selected photoluminescent fluorescentmaterials absorb incident activating electromagnetic radiation, forexample, ultraviolet, visible and/or infrared portions of theelectromagnetic spectrum and an electron is excited from a ground stateinto an excited state. In the case of such photoluminescent fluorescentmaterials the electron returns rapidly to the ground state withsubsequent release of electromagnetic radiation, for example,ultraviolet, visible and/or infrared radiation. The time for emission tooccur from the excited state in photoluminescent fluorescent materialscan be on the order of 10⁻⁸ seconds. Continued emission fromphotoluminescent fluorescent materials ceases when the activating energyceases. The energy of the emission is generally lower than the energy ofthe incident activating radiation.

Selected photoluminescent fluorescent materials useful in the currentinvention include photoluminescent fluorescent materials that absorb inthe visible and/or infrared and emit in the visible and/or infrared. Forexample, photoluminescent fluorescent materials that absorb in thevisible and emit in the visible include, for example, coumarins such ascoumarin 4, coumarin 6, and coumarin 337; rhodamines such as rhodamine6G, rhodamine B, rhodamine 101, rhodamine 19, rhodamine 110, andsulfarhodamine B; phenoxazones including Nile red and cresyl violet;styryls; carbostyryls; stilbenes; and fluorescenes. Examples ofphotoluminescent fluorescent materials that absorb in the visible regionof the electromagnetic spectrum and emit in the far visible and infraredregions include, for example, Nile Blue, IR 140 (CAS#53655-17-7), IR 125(CAS#3599-32-4), and DTTCI (CAS#3071-70-3). Below in Table 1 are theabsorption and emission characteristics of some of the photoluminescentfluorescent materials suitable for the current invention.

TABLE 1 Max. Fluorescent CAS # Absorbance (nm) Max. Emission (nm)Coumarin 6 38215-35-0 458 505 Rhodamine 110 13558-31-1 510 535 Rhodamine19P 62669-66-3 528 565 Rhodamine 6G 989-38-8 530 556 Nile red 7385-67-3550 650 Nile blue 53340-16-2 633 672 IR 676 56289-64-6 676 720 IR-676 is1,1′,3,3,3′,3′-Hexamethyl-4,5,4′,5′-dibenzoindodicarbocyanine

When photoluminescent phosphorescent materials are admixed with selectedphotoluminescent fluorescent materials, the emission of thephotoluminescent phosphorescent materials can be absorbed by thephotoluminescent fluorescent materials with subsequent emission whichexhibit a downward Stokes shift to energy lower than the energy used toexcite the photoluminescent phosphor. The emission energy from thephotoluminescent fluorescent material can be absorbed by a secondphotoluminescent fluorescent material selected for its ability to absorbsuch radiation. The second photoluminescent fluorescent material willexhibit a downward Stokes shift to energy lower than the energy emittedfrom the first photoluminescent fluorescent material. Additionalphotoluminescent fluorescent materials can be chosen to further exhibitStokes shifts until a selected emission is achieved. The selectedemission can be chosen to be partially or fully in the infrared regionsof the electromagnetic spectrum. Generally, a Stokes shift for a singlephotoluminescent phosphorescent or photoluminescent fluorescent materialranges from 20 to 100 nm. In order to produce longer Stokes shifts,multiple photoluminescent fluorescent materials can be used to produce acascading Stokes shift. A cascading Stokes shift is produced bysuccessive absorptions of the emission of one of the photoluminescentmaterials by another of the photoluminescent fluorescent materials andre-emission at a longer wavelength. When done multiple times Stokesshifts significantly in excess of 50 nm can be created.

The photoluminescent phosphorescent materials and the photoluminescentfluorescent materials may be admixed or they may be separated intodifferent layers with the layer containing the fluorescent materialsituated outwardly toward the observer. Activating energy penetrates theouter fluorescent surface to activate the phosphorescent materials belowwhose emission activates the fluorescent material in the outer layer.

The quantum efficiency of compositions comprising photoluminescentphosphorescent and/or photoluminescent fluorescent materials will bedependent on a number of factors, such as degree of overlap between theemission spectrum of one of the photoluminescent materials with theabsorption spectrum of another of the photoluminescent materials and thedegree to which the photoluminescent fluorescent materials aremolecularly dispersed in the polymer comprising the binding matrix. Inorder for the photoluminescent fluorescent materials to be molecularlydispersed in the polymer or exist as a solid state solution in thechosen polymer or polymers, it is essential for the photoluminescentfluorescent materials to be in solution in the liquid carrier medium andbe compatible with the chosen polymers.

Selected admixing of photoluminescent phosphorescent materials withphotoluminescent fluorescent materials, or layers made therefrom, willresult in compositions that can be charged or activated by incidentelectromagnetic energy, for example, by ultraviolet, visible, orcombinations thereof, and emit partially or fully in the infrared. Sincethe activated photoluminescent phosphorescent material will continue toemit radiation long after the activating radiation has been removed, thephotoluminescent composition will continue to emit radiation partiallyor fully in the infrared region of the electromagnetic spectrum.

It can readily be seen that activation of the inventive fibers anddetection of their subsequent emission can occur at separate times andat separate places. Thus, the fibers, fabrics made therefrom, andobjects containing the fiber can be charged with electromagneticradiation. The radiation can be shut off and the fibers, fabrics madetherefrom, and objects containing the fiber can be moved to a differentplace while the emissions continue to occur enabling detection to occurlong after activation has ceased.

Selected photoluminescent fluorescent materials can additionally beincorporated into the photoluminescent compositions containing the abovedescribed photoluminescent phosphorescent and photoluminescentfluorescent materials to optimally couple the excitation source and theabsorbance spectrum of a selected photoluminescent material that is tobe initially activated from an external electromagnetic radiationsource.

The photoluminescent fluorescent materials of the current invention thatexhibit this property can be admixed into the photoluminescentcomposition containing the phosphorescent materials or they can residein a fiber sheath coating either above or below such photoluminescentcomposition, or both.

For optimal performance of luminescent materials for high intensity andpersistence, specific photoluminescent materials and mixtures of suchmaterials need to be adapted for use in varying conditions, for example,excitation conditions or environmental considerations. Water-resistantcompositions suitable for protecting the photoluminescent phosphorescentparticles and compositions that minimize photolytic degradation aresought-after. Beyond the selection of the photoluminescentphosphorescent materials and/or any additional photoluminescentfluorescent materials used to enhance their performance, it should benoted that the emission intensity and/or persistence from aphotoluminescent composition is greatly affected by both the way inwhich the photoluminescent phosphorescent materials are distributed andthe additives used, as well as the manner in which that composition isapplied.

The improper selection and use of the composition materials, such asbinders, dispersing agents, wetting agents, rheology modifiers,photostabilizers, and the like can diminish the emission intensityemanating from the composition. This can occur, for example, due toagglomeration or settling of photoluminescent phosphorescent particles,either during handling of the formulated materials or after applicationof the formulated materials. The reduction in emission intensity and/orpersistence can result from incomplete excitations and/or scattering ofemitted radiation. The scattering of photoluminescent emissions can beeither due to agglomeration of photoluminescent phosphorescent materialor as a consequence of electromagnetic radiation scattering by one ormore of the additives selected to stabilize the photoluminescentphosphorescent pigment dispersion. The net result will be lower emissionintensity and persistence.

The use of colorants in the form of pigments that are absorptive ofvisible electromagnetic radiation, in order to impart daylight color tophotoluminescent compositions, even when such pigments are notabsorptive of photoluminescent emissions, can result in degradation ofphotoluminescent intensity and persistence by virtue of eitherscattering of photoluminescent emissions or by inadequate charging ofphotoluminescent phosphorescent materials. Hence, for attaining maximumemission intensity, use of absorptive pigments should be avoided. Itshould be noted however that creation of stealth markings can be aidedby the selective use of absorptive pigments designed to adjust thedaylight color of the markings so that a photoluminescent marking willblend in with the surrounding areas so as to be unnoticeable undernormal conditions. By keeping the amount of pigment used low, one canminimize any negative impact on the emission intensity and persistenceof the emission signature.

As mentioned earlier, for stealth identification the emission is notordinarily observable by a human observer. It should be noted, however,that there is a wide range of capability in humans for the detection ofvisible radiation. Hence, for highly sensitive applications, wherein itis desirable that there be no circumstance wherein even a human observerwith acute vision cannot detect any emission, even after long adaptationto nighttime conditions, and standing very close to the object with thephotoluminescent marking, one can ensure a high degree of stealthdetection by incorporating a visible light absorptive pigment, either inthe photoluminescent fiber cores or in a sheath layer over thephotoluminescent fiber core.

It is important to select only those polymeric binder resins for thephotoluminescent materials that do not absorb electromagnetic radiationwithin the excitation spectrum of the chosen photoluminescent materialand that are also compatible with the selected photoluminescentmaterials. This is important, for otherwise, the excitation of thephotoluminescent materials will be inhibited. It is also desirable thatthe chosen polymeric materials should have minimal impact on theemission intensity, that is, it should not exhibit any significantquenching of the photoluminance. Binder resins suitable for theinventive compositions include acrylates, for example NeoCryl® B-818,NeoCryl® B-735, NeoCryl® B-813, and combinations thereof, all of whichare solvent soluble acrylic resins available from DSM NeoResins®,polyvinyl chlorides, polyurethanes, polycarbonates, polyesters, andnylons such as Nylon 6 or Nylon 6,6 and combinations thereof.

The photoluminescent materials may also be included in fiber-glassand/or polysiloxane constructions both as a blend and in core/sheath orother fiber applications.

The liquid carrier can be, for example, any solvent which does notadversely impact the photoluminescent materials and which allows for thesolubility of the photoluminescent fluorescent materials selected forthe photoluminescent composition. In selecting the liquid carrier, forcases wherein the polymer is soluble in the liquid carrier, thepolymeric solution should be clear and should not exhibit any haze,otherwise, emission intensity transmission will be adversely impacted.In general, highly polar solvents will increase the likelihood ofemission quenching, and hence should, in general, be avoided. Suitableliquid carriers include glycols, glycol ethers, glycol acetates,ketones, hydrocarbons such as toluene and xylene.

Photostabilizers useful in the inventive composition include UVabsorbers, singlet oxygen scavengers, antioxidants, and or mixtures, forexample, Tinuvin® 292, Tinuvin® 405, Chimassorb® 20202, Tinuvin® 328, orcombinations thereof, all from Ciba® Specialty Chemicals.

Suitable rheology modifiers include polymeric urea urethanes andmodified ureas, for example, BYK® 410 and BYK® 411 from BYK-Chemie®.

Dispersants suitable for the inventive compositions include acrylicacid-acrylamide polymers, salts of amine functional compounds and acids,hydroxyl functional carboxylic acid esters with pigment affinity groups,and combinations thereof, for example DISPERBYK®-180, DISPERBYK®-181,DISPERBYK®-108, all from BYK-Chemie® and TEGO® Dispers 710 from DegussaGmbH.

Other additives can be incorporated into the inventive compositions,including wetting agents such as polyether siloxane copolymers, forexample, TEGO® Wet 270 and non-ionic organic surfactants, for exampleTEGO® Wet 500, and combinations thereof; and including deaerators anddefoamers such as organic modified polysiloxanes, for example, TEGO®Airex 900.

According to the present photoluminescent compositions components can befrom about 10%-50% of binder resin, about 15%-50% of liquid carrier,2%-35% photoluminescent phosphorescent material, 0.5%-5.0% dispersingagent, 0.2%-3.0% rheology modifying agent, 0.1%-3.0% photostabilizer,0.2%-2.0% de-aerating agent, 0.2%-3.0% wetting agent, and 0.1%-2.0%photoluminescent fluorescent material.

Fibers of the current invention may be made by any of the known methodsof fiber manufacture including solution spinning, melt spinning, meltextrusion and injection molding. In the current invention a monofilamentfiber may be spun from a fiber composition containing bothphotoluminescent phosphorescent materials and photoluminescentfluorescent material. In the current invention the fiber may be formedinto a core/sheath configuration in which the core contains both thephotoluminescent phosphorescent and the photoluminescent fluorescentmaterials and other components of the composition, as described above,and the sheath contains the same composition, or a differentcomposition, but without any photoluminescent materials. The core maycontain only photoluminescent phosphorescent materials and the sheathmay contain the photoluminescent fluorescent materials. The core maycontain both photoluminescent phosphorescent materials andphotoluminescent fluorescent material while the sheath may also containphotoluminescent fluorescent materials. Some of the fluorescentmaterials may absorb charging radiation and emit radiation useful incharging the photoluminescent phosphor materials in the core, which thenemit radiation that the fluorescent materials use to give an infraredemission signature. In each of these constructions the photoluminescentmaterials are chosen such that, as described above, the emissionsignature is fully or partially in the infrared region of theelectromagnetic spectrum.

The sheath may also contain optimized amounts of colorant in order forthe fiber to blend in with other fibers, or object materials, with whichthe fiber will be associated, so as not to be visibly distinguishablefrom them.

Other fiber constructions of the current invention include an inner coreof a core/sheath/sheath construction containing non-photoluminescentmaterials such as a conductive core, a fiber strengthening core, afiberglass core, a reflective core or other core composed of materialsdesigned to give desirable characteristics to the fiber. The firstsheath can be composed of one of the photoluminescent compositions useddescribed above which were used in the core and the second sheath can becomposed of one of the sheath materials described above, eitherphotoluminescent or non-photoluminescent.

All of the fibers of the current invention as described above may alsoinclude a further sheath onto the core/sheath or core/sheath/sheathconstructions designed to give desirable characteristics to the fibersuch as mechanical strength, abrasion resistance, visible colorationdesirable for certain applications such as, for example, blendinginconspicuously with other fibers; protection of the fiber, such as, forexample, from chemicals or moisture and from photolysis; and enhanceddaylight visibility of the infrared emission signature. It should benoted that, for highest efficiency, the emission from the fiber isdirected outwardly from the fiber and not length-wise down the fiber asis typical of fiber optical constructions. Thus the refractive indexdifferences between the core and all the sheaths should be kept to aminimum.

The core may be an optical fiber around which is coated the varioussheaths of photoluminescent compositions, as described above, to providefor another embodiment of the inventive fibers.

Fibers of other configurations are suitable for the current invention.For example, island-in-the-sea can be composed of island fiber whereinone or more of the island fibers contain both photoluminescentphosphorescent materials and photoluminescent fluorescent material whilethe sea may also contain non-luminescent materials, or the islandcontain only the photoluminescent phosphorescent materials and the seacontains the photoluminescent fluorescent materials. However the islandsmay contain both photoluminescent phosphorescent materials andphotoluminescent fluorescent material while the sea may containphotoluminescent fluorescent materials. The photoluminescent materialsare chosen such that, as described above, the emission signature isfully or partially in the infrared region of the electromagneticspectrum. Some of the fluorescent materials may absorb chargingradiation and emit radiation useful in charging the photoluminescentphosphor materials in the core, which then emit radiation that the chainof fluorescent material uses to give an infrared emission signature. Inother configurations, some of the islands may be non-luminous but areincluded to provide other desirable fiber characteristics, such sstrength, conductivity and the like.

While these configurations are just a few examples of fiberconstructions of the current invention, other configurations in whichphotoluminescent phosphorescent materials and the photoluminescentfluorescent materials are in the same composition, or separated inmulticomponent configurations or the photoluminescent phosphorescentmaterials and the photoluminescent fluorescent materials are in the samecomposition and additional photoluminescent materials are present inother portions of the multicomponent fiber, the end result is anemission signature fully or partially in the infrared region of theelectromagnetic spectrum.

Methods to prepare photoluminescent fabrics or objects containing thefabric or fibers using the present inventive compositions and which emiteither wholly or partially in the infra red can encompass a variety oftechniques for application of the photoluminescent fibers describedabove either onto or into fabrics or objects. For example, techniqueswherein the compositions described above can be applied into fabricsinclude weaving the fibers using a number for processes readily knownthe art. Further the fiber may be woven into the fabric along withnon-luminescent fibers to give a fabric with a known, predeterminedphotoluminesce pattern fully or partially in the infrared. Fibers may beused to embroider a pattern, mark, identification, etc onto or into afabric or other substrate.

Photoluminescent fibers, fabrics made therefrom, and objects containingthe fiber and which emit either wholly or partially in the infra red canalso be prepared by incorporating the fibers, described above, into theobjects by including the photoluminescent fibers in the manufacture ofthe object. For example, for plastic objects that can be prepared byextrusion, any of the fibers described above can be added to theobject's composition at from 2 to 30% of the total composition andextruded to give an object which can be identified or detected by theinventive method. Preparation of photoluminescent objects wherein thefibers are included in the manufacture of the object can include avariety of manufacturing techniques such as molding, extrusion, etc. Forpurposes of identification, detection and authentication, an object needonly be partially coated with the photoluminescent composition.

The inventive fibers may be chopped into smaller pieces and combinedwith other materials and processed to provide objects thatphotoluminesce fully or partly in the infrared portion of theelectromagnetic spectrum.

The above described photoluminescent fibers, fabrics made therefrom, andobjects containing the fiber can be charged or activated withelectromagnetic radiation, for example, ultraviolet, near ultraviolet orcombinations thereof, by a number of convenient methods including metalhalide lamps, fluorescent lamps, or any light source containing asufficient amount of the appropriate visible radiation, UV radiation orboth, as well as sunlight, either directly or diffusely, including suchtimes when sunlight is seemingly blocked by clouds. At those timessufficient radiation is present to charge or activate the fibers,fabrics made therefrom, and/or objects containing the fiber. The sourceof activation can be removed and the fibers, fabrics made therefrom,and/or objects containing the fiber will continue to emit radiation inthe selected region and be detected, for example, in darkness when thereis no activating radiation.

It should be clearly pointed out that the photoluminescent fibers,fabrics and objects made therefrom enable spatial and temporaldecoupling of the photoluminescent layer and enables stealth detection.When these marking, whether stealth or not, are activated, emissioncontinues long after the activating energy has been removed or turnedoff, allowing for detection to occur at a later time, and under stealthconditions. Because the emission continues after activation, themarking, or object containing the marking, can be moved far away fromthe activating source and detected under stealth conditions, that is,the marking does not need to be activated during detection andfurthermore the emission from the marking is not detectable with thenaked eye.

Since the fibers, fabrics made therefrom, and/or objects containing thefiber will continue to emit the desired radiation, charging of thefibers, fabrics made therefrom, and/or objects containing the fiber anddetection of the emission signature are spatially and temporallydecoupled, that is, the detection step can occur at a time and placeseparate from the activation step. This allows the fibers, fabrics madetherefrom, and/or objects containing the fiber either to be charged andremoved from the site of activation or to be charged with subsequentremoval of the charging source. Further, detection can occur at adistance from the fibers, fabrics made therefrom, and/or objectscontaining the fiber object and/or the activating source.

For the purpose of identification or authentication, a detector thatwill detect the selected emission signature from the photoluminescentfibers, fabrics made therefrom, and/or objects containing the fiber isused. Such detectors may or may not have capability of amplifying thephotoluminescent emissions. An example of a detection apparatus withamplification is night vision apparatus. Night vision apparatus candetect either visible radiation if present, infrared radiation, or bothvisible and infrared radiation. The detection apparatus can be designedto detect specific emission signatures. Where necessary, detectors canincorporate amplification capabilities. The detector can be designed toread a specific wavelength of the emission signature or the fibers,fabrics made therefrom, and/or objects containing the fiber can becreated to emit radiation suitable for a specific detector. Because ofthe nature of the methods and fibers of the current invention, detectioncan occur at a time and place separate from activation.

Under certain conditions the detection equipment may be adverselyimpacted by radiation from extraneous sources causing identification ordetection of the intended fibers, fabrics made therefrom, and/or objectscontaining the fiber to be difficult due to the inability of thedetector to differentiate between emission signature and such spuriousradiation. Under these conditions, the detection equipment, for example,night vision apparatus, may be fitted with a filter designed toeliminate the extraneous visible radiation thereby enhancingidentification or detection.

The type of image obtained from the selected emission signature can bein the form of a general imaging emitted by the fibers, fabrics madetherefrom, and/or objects containing the fiber or it may be in the formof a pattern in the fabric or objects containing the fiber. It can alsohave informational properties in the form of alphabetical, numerical, oralpha-numeric markings as well as patterns and symbols, such asgeometric shapes and designations. In this manner, identification ordetection can be topical, either with up-to-date information, such astimes and dates, as well as messages.

Identification or detection methods are inclusive of both those methods,wherein the photoluminescent fibers, fabrics made therefrom, and/orobjects containing the fiber are used to create photoluminescentmarkings which enable the emission signature and may be detectable by ahuman observer and those methods wherein such emissions from suchphotoluminescent markings are stealth to enable “clandestine” or“stealth” detection. When practicing stealth identification, for thecase wherein the emission is only partially in the infrared region ofthe electromagnetic spectrum, the visible emission component is lowenough to be undetectable by a human observer. Identification ordetection of the stealth markings described above, either for fibers,fabrics made therefrom, or objects containing the fiber can only be madeby using devices designed to detect the selected emission signature.

Identification or detection methods using the current inventive fibers,fabrics made therefrom, and/or objects containing the fiber andembodying clandestine detection can be deployed for detection oridentification of objects, people or animals. Photoluminescent fibers,fabrics made therefrom, and/or objects containing the fiber onto or intowhich such photoluminescent markings can be applied include, forexample, military objects to designate friend or foe, as well as trailmarkings. Such markings are designed to be detected only by selectedpersonnel. Examples of the use of markings for stealth detection includeairplane or helicopter landing areas, or markings that reveal thepresence or absence of friendly forces.

Identification or detection methods using the current inventive fibers,fabrics made therefrom, and/or objects containing the fiber andembodying both clandestine and non-clandestine markings allow foridentification of, for example, stationary combat apparatus, mobilecombat apparatus, combat articles of clothing or combat gear either wornby combatants or carried by combatants, tanks, stationary artillery,mobile artillery, personnel carriers, helicopters, airplanes, ships,submarines, rifles, rocket launchers, semi-automatic weapons, automaticweapons, mines, diving equipment, diving clothing, knap-sacks, helmets,protective gear, parachutes, and water bottles.

Identification or detection methods using the current inventive fibers,fabrics made therefrom, and/or objects containing the fiber andembodying both stealth and non-stealth markings allow for identificationof, for example, stationary combat apparatus, mobile combat apparatus,combat article of clothing, or combat gear either worn by combatants orcarried by combatants, tank, stationary artillery, mobile artillery,personnel carriers, helicopters, airplanes, ships, submarines, rifles,rocket launchers, semi-automatic weapons, automatic weapons, mines,diving equipment, diving clothing, knap-sacks, helmets, protective gear,parachutes, and water bottles.

The current fibers, fabrics made therefrom, and/or objects containingthe fiber allow for identification or detection including tagging,tracking and locating transportation vehicles, for example, buses,airplanes, taxi cabs, subway vehicles, automobiles and motorcycles.

Identification or detection methods, using the current inventive fibers,fabrics made therefrom, and/or object containing the fiber and embodyingeither stealth or non stealth markings, can also be used forapplications such as in sports and entertainment, for example, inhunting and fishing applications which are designed to identify ordetect other hunters or fisherman. Stealth markings can be particularlyuseful in hunting applications such as vest, pants, shirt or jacket andthe like, wherein accidents can be avoided by using infrared emissiondetection apparatus for identifying or detecting other hunters but atthe same time since no visible emission is detectable, avoiding spookingthe hunted animal.

Identification or detection compositions that embody stealth markingsmay be particularly useful for applications requiring security.

The fibers, fabrics made therefrom, and/or object containing the fiberof the current invention can also be used in anti-counterfeitapplications applicable to a wide variety of goods or objects.Photoluminescent fibers, fabrics made therefrom, and/or objectcontaining the fiber prepared according to the methods described abovecan be utilized in anti-counterfeit applications, for example, currency,anti-piracy applications, such as CDs or DVDs, luxury goods, sportinggoods etc. In many of these applications it becomes important that thepotential counterfeiter be unaware that the object that is beingcounterfeited contains a fiber, a fabric made therefrom, and/or objectcontaining the fiber that will authenticate the object. The clandestinemarking can also be coded such as a date code or other identifying codethat a counterfeited object would not have.

The current fibers, fabrics made therefrom, and/or object containing thefiber can be applied onto carrier materials, such as films, for example,polyester, polycarbonate, polyethylene, polypropylene, polystyrene,rubber or polyvinyl chloride films, or metallic plates, for example,aluminum, copper, zinc, brass, silver, gold, tin, or bronze plates.Other layers can be added to the carrier material such as an adherentmaterial, for example, an adhesive with high or low peel strength or amagnetic material. The carrier material with the photoluminescentfibers, fabrics made therefrom, and/or objects containing the fiberapplied thereon can either be attached permanently to an object or itcan be transferable so that identification or detection can be changed,updated or removed. Such application allows for an object to have theidentification or detection capabilities of the current inventionwithout the object itself undergoing a fabrication process. In thisapplication, if information becomes outdated, the carrier material withthe photoluminescent fibers, fabrics made therefrom, and/or objectscontaining the fiber applied thereon in the form of a removable film orplate can be replaced by another carrier material with thephotoluminescent fibers, fabrics made therefrom, and/or objectscontaining the fiber applied thereon with updated information, forexample, in safety applications or security applications.

The current fibers, fabrics made therefrom, and/or objects containingthe fiber allow for creation of photoluminescent objects wherein atleast some of the photoluminescent fluorescent materials areincorporated in a second photoluminescent layer either above or below afirst photoluminescent layer, such first photoluminescent layercomprising photoluminescent phosphorescent materials or photoluminescentphosphorescent and photoluminescent fluorescent materials with the netemission from the object being either wholly or partially in the infrared. It should be noted that such second photoluminescent layers canalso serve as a protective coating for the first photoluminescent layer.The fibers, fabrics or compositions containing the fiber can be utilizedin any of the layers above.

Objects prepared using the current inventive fibers, fabrics madetherefrom, and/or objects containing the fiber can have low emissionintensity by virtue of inadequate reflection of the emittedelectromagnetic radiation; either because of surface roughness orbecause of materials in the object that are absorptive of the selectedemission signature. As a result reflective layers or coatings that arereflective of the emissions from the photoluminescent compositions canbe used as primers to provide a surface from which the emissionsignature can reflect. Hence a reflective layer may be first appliedeither onto a carrier material or onto the object itself followed by oneor more photoluminescent layers containing the fibers, fabrics madetherefrom, and/or objects containing the fiber of the current invention.

Further, certain usages of these fibers, fabrics made therefrom, and/orobjects containing the fiber in which adverse environmental conditionsare present require protection, for example, protection from wetconditions, resistance to mechanical abrasion, and improved robustness.In these applications use of a protective layer or sheath can be highlybeneficial. A protective sheath may also be prepared containinganti-photolysis materials that are designed to protect the underlyingphotoluminescent materials. Additionally the protective top-coat can beapplied to objects that have a reflective coating as described above.Such protective top coats may also comprise some or all of thephotoluminescent fluorescent materials.

1. A photoluminescent fiber comprising: a) one or more photoluminescentphosphorescent materials and, b) one or more photoluminescentfluorescent materials; wherein the one or more photoluminescentphosphorescent materials absorb and emit electromagnetic energies whencharged or activated by electromagnetic radiation from an excitationsource incident upon the one or more phosphorescent materials, andwherein the one or more photoluminescent fluorescent materials absorbthe emission from the one or more photoluminescent materials and emitelectromagnetic energies to give a selected emission signature, thephotoluminescent materials being selected so that the emission of one ofthe photoluminescent materials overlaps with the absorbance of anotherof the photoluminescent materials, wherein the selected emissionsignature is the emission from one or more of the selectedphotoluminescent fluorescent materials, such emission being essentiallyunabsorbed by any of the other photoluminescent materials.
 2. The fiberof claim 1, wherein the selected emission signature lies at least in aportion of the visible electromagnetic spectrum.
 3. The fiber of claim1, wherein the fiber comprises a core and a first sheath and wherein thecore is comprised of one or more of the photoluminescent phosphorescentmaterials and, optionally, one or more of the fluorescent materials, andthe sheath is comprised of one or more of the photoluminescentfluorescent materials.
 4. The fiber of claim 3, further comprising asecond sheath comprised of one or more of the photoluminescentfluorescent materials.
 5. The fiber of any one of claims 1-4, furthercomprising an outer sheath, wherein the outer sheath comprises at leastone of color shifting components, color masking components, fiberprotecting components, or anti-photolysis components.
 6. A fabric madefrom the fiber of claim
 5. 7. A photoluminescent fiber comprising: a)one or more photoluminescent phosphorescent materials and, b) one ormore photoluminescent fluorescent materials; wherein the one or morephotoluminescent phosphorescent materials absorb and emitelectromagnetic energies when charged or activated by electromagneticradiation from an excitation source incident upon the one or morephosphorescent materials, and wherein the one or more photoluminescentfluorescent materials absorb the emission from the one or morephotoluminescent materials and emit electromagnetic energies to give aselected emission signature, the photoluminescent materials beingselected so that the emission of one of the photoluminescent materialsoverlaps with the absorbance of another of the photoluminescentmaterials, wherein the selected emission signature is the emission fromone or more of the selected photoluminescent fluorescent materials, suchemission being essentially unabsorbed by any of the otherphotoluminescent materials, and wherein the core is reflective of thephotoluminescent emission, a strengthening fiber, a conductive fiber oran optical fiber.
 8. The fiber of claim 7, wherein the selected emissionsignature lies at least in a portion of the visible electromagneticspectrum.
 9. The fiber of claim 7, wherein the fiber further comprises asecond sheath and wherein the first sheath is comprised of one or moreof the photoluminescent phosphorescent materials and optionally one ormore of the fluorescent materials and the second sheath is comprised ofone or more of the photoluminescent fluorescent materials.
 10. The fiberof claim 9, further comprising a third sheath comprised of one or moreof the photoluminescent fluorescent materials.
 11. The fiber of any oneof claims 7-10, further comprising an outer sheath, wherein the outersheath comprises at least one of color shifting components, maskingcomponents, or fiber protecting components.
 12. A fabric made from thefiber of claim 11.